<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>字体</title>
    <style>
        h3 {
            font-size: 50px;
            font-weight: 700;
            text-align: center;
        }
        h4 {
            color: red;
            font-size: 30px;
        }
        h5 {
            color: #00ff00;
            font-size: 20px;
        }
        h6 {
            color: rgb(0,0,255);
            font-size: 10px;
        }
        p {
            font-size: 50px;
            color: coral;
        }
    </style>
</head>
<body>
    <h3>这是三级标题</h3>
    <h4>color</h4>
    <h5>color</h5>
    <h6>color</h6>
    <p>默认字体大小是16px，修改后为50px。</p>
</body>
</html>